Year mm per year 1962 2880 1963 2880 1964 2880 1965 2880 1966 2880 1967 2880 1968 2880 1969 2880 1970 2880 1971 2880 1972 2880 1973 2880 1974 2880 1975 2880 1976 2880 1977 2880 1978 2880 1979 2880 1980 2880 1981 2880 1982 2880 1983 2880 1984 2880 1985 2880 1986 2880 1987 2880 1988 2880 1989 2880 1990 2880 1991 2880 1992 2880 1993 2880 1994 2880 1995 2880 1996 2880 1997 2880 1998 2880 1999 2880 2000 2880 2001 2880 2002 2880 2003 2880 2004 2880 2005 2880 2006 2880 2007 2880 2008 2880 2009 2880 2010 2880 2011 2880 2012 2880 2013 2880 2014 2880 2015 2880 2016 2880 2017 2880 2018 2880 2019 2880 2020 2880